This invention generally relates to the field of electromagnetic devices, and more particularly, is directed to a low profile electromagnetic linear motion device.
Electromagnetic devices are widely used to provide on demand remote movement of mechanical devices. For example, solenoids are commonly employed to impart motion to a mechanical device by the application of an electric current. The typical solenoid comprises one or more electric coils wound around a core. When an electric current is applied to the coil, an electromagnet is formed having a North pole and a South pole as is well known in the art. Magnetic lines of flux flow between the two poles and any ferrous metal which the lines of flux cut across will be attracted to the electromagnet. The amount of attractive force generated by the magnet is proportional to flux density. Flux density is a function of both the number of turns in the coil of the magnet and the amount of current flowing through the coil. The greater the number of turns and/or the larger the current flow, the greater the flux density and thus, the greater the attractive force.
In most practical applications, the amount of current available to flow through the coils is usually fixed by the power source and cannot be readily changed. Thus, when additional attractive force is required, the number of turns in the coil must be increased. Increasing the number of turns, however, correspondingly increases the size of the device. In many applications, size is an important consideration. Thus, electromagnetic devices known in the prior art are deficient in this respect.
An electromagnetic device typical of those known in the prior art is disclosed in U.S. Pat. No. 3,504,315 issued in the name of Stanwell. This device is cylindrical in shape and comprises first and second electromagnetic coils wound around a cavity which receives an armature. When the coils are energized, the armature travels within the cavity dependent on the direction of current flow through the coils. The motion of the armature is transmitted to a rod which imparts motion to an external device. Increasing the number of turns in the coils to provide additional force increases the diameter of the device.
Electromagnetic devices of the type disclosed by Stanwell are often used to control the power door lock system in automobiles. A solenoid or actuator is installed in each door panel for operating the door lock mechanism. In modern automobiles, the thickness of the door panels are becoming increasingly thinner. Thus, the solenoids which operate the door lock system must be made corresponding thinner. In solenoids known in the prior art, such as the one disclosed by Stanwell, reducing the thickness of the solenoid to allow it to fit in a confined space, such as modern-day automotive door panels, also reduces its pushing and pulling force. Accordingly, such devices are also deficient in this respect.